1. The Field of the Invention
The present invention relates generally to semiconductor device testing during fabrication. More particularly, the present invention relates to a system and method that employs a cleaning wafer for in-line cleaning of probe pins on a probe card used in testing semiconductor devices during fabrication.
2. The Relevant Technology
During fabrication of semiconductor devices from silicon wafers, a prober machine is used to interface a semiconductor device to a tester machine while still in wafer form prior to cutting the wafer into individual chips. A typical prober machine includes a probe card having an array of probe pins that contact bond pads on the semiconductor device during testing. The bond pads on the semiconductor device are made from metallic materials such as aluminum which can oxidize when exposed to air. Also, organic material left over from certain fabrication processes can be disposed on the bond pads. When probe pin tips repeatedly contact bond pads on a silicon wafer, metal oxides such as aluminum oxides and other materials on the bond pads can build-up on the probe pin tips, thereby interfering with the function of the probe pins during testing operations. Thus, it becomes necessary to periodically clean the probe pins on a probe card.
In conventional cleaning operations, a probe maintenance station is utilized in order to clean probe pins on a probe card used in testing fabricated semiconductor devices. This requires the removal of the probe card from the production line in order to clean the probe pins, resulting in a certain amount of production downtime. The production downtime includes the time to remove the probe card from the prober, and the time to install and perform a complete new set up for a clean probe card. Also, additional time is spent in taking the dirty probe card to a hardware support facility, in cleaning/aligning, and documenting the probe card, and in getting the cleaned probe card back to production personnel.
As manufacturing techniques have improved, it has become possible to probe more semiconductor dies in parallel at one time, requiring increasingly wider probe card arrays. This has resulted in ever increasing difficulty and downtime in order to have the probe card arrays taken off-line, to replace the probe card arrays, and then to bring the system back on-line, as well as additional time to clean the removed probe card arrays and bring the arrays back into service. While various ceramic burnishing chucks have been used in the past to clean probe tips, such as separate chucks with a piece of ceramic thereon for the probes to touch down on for cleaning, such conventional burnishing chucks are too small for the wider probe cards currently used.
Accordingly, there is a need for improved probe pin cleaning systems and methods that overcome or avoid the above problems.
The present invention is directed to a system and method that employs a cleaning wafer such as a ceramic wafer disc for in-line cleaning of probe pins on a probe device such as a probe card in a prober machine used in testing semiconductor devices during fabrication. The shape and thickness of the cleaning wafer is similar to a silicon production wafer, allowing the cleaning wafer to be inserted in place of the silicon production wafer in order to perform a cleaning cycle for the probe pins without having to remove the probe card from a production line. The cleaning wafer is used to make contact with the probe pin tips and remove any buildup of oxides or other undesired substances that tend to accumulate on the probe pin tips. The same apparatus used to test production wafers also handles the cleaning wafer during a probe cleaning cycle.
During operation of the cleaning cycle, the cleaning wafer is placed in a manual load tray or auxiliary tray, which inserts the cleaning wafer into a prober machine. The cleaning wafer is transported by a robotic trolley to a prealign stage area where the cleaning wafer is aligned and centered. The cleaning wafer is then placed on a support device. The support device and cleaning wafer are positioned under a pneumatic sensor and profiled to determine wafer planarity. The support device and cleaning wafer are then positioned underneath the probe pins on the probe card to be cleaned. Thereafter, the z-axis distance between the probe pins and the surface of the cleaning wafer is decreased such that the probe pins contact the cleaning wafer. The probe pins can be repeatedly contacted with the cleaning wafer to remove unwanted debris from the probe pins. The cleaning wafer is removed from the support device and prober machine when cleaning of the probe pins has been completed.
The cleaning wafer preferably has a substantially circular shape and blocks transmission of nonionizing electromagnetic radiation energy therethrough such as infrared light energy. In one embodiment, the cleaning wafer has a first abrasive surface made of a ceramic material capable of removing unwanted debris from a probe tip, and a second opposing surface having an opaque coating thereon capable of blocking transmission of infrared light energy through the wafer. An outer periphery between the first and second surfaces has a notch formed therein to allow proper alignment of the cleaning wafer when loaded into the prober machine.
The present invention allows probe pins on a probe card to be effectively cleaned while still installed in a prober machine, thereby eliminating the need to remove the probe card, reinstall a clean probe card, and rerun a complete new set-up for the clean probe card. This results in a reduction in production downtime.
Other aspects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.